Coupled control of operating parameters of an incubator

Abstract

The invention is directed to a method for controlling the operating parameters determining the thermal metabolism of a premature or newborn disposed in an incubator. These operating parameters include the incubator air temperature and the incubator humidity. The method is improved in such a manner that the adjustment of the parameters is coupled to the combination thereof optimizing the thermal metabolism without the necessity of a complex multiple step adjustment for each individual parameter. The method is characterized in that a primary control circuit for controlling the first parameter supplies the actual value corresponding thereto as a control parameter to a logic generator which determines a sequence value by means of a logic function. This sequence value is conducted to a secondary circuit as a desired value for the adjustment of the second parameter.

What is claimed is: 
     
       1. An incubator for controlling an environment for an infant, the incubator comprising: a housing having a base and an enclosure mounted on said base for defining an enclosed space adapted to the infant and wherein the environment for the infant is controlled;   said housing defining an equipment compartment;   circulating means mounted in said equipment compartment for circulating incubator air through said enclosed space;   first parameter means for imparting a first physical change to the environment within said enclosed space measurable as a first operating parameter of said environment;   second parameter means for imparting a second physical change to the environment within said enclosed space measurable as a second operating parameter of said environment;   sensing means for sensing said first operating parameter and for supplying a first signal indicative of the actual value of said first operating parameter;   desired value generator means for supplying a second signal indicative of a desired value of said first operating parameter;   primary control circuit means for comparing said first and second signals and for driving said first parameter means to set and maintain said first operating parameter in dependence upon the comparison of said first and second signals;   logic generator means for defining a functional relationship between said first and second operating parameters;   said logic generator means being connected to said primary control circuit for receiving one of said first and second signals as a control value and for generating an output sequence signal based on said functional relationship and said control value with said output sequence signal defining a desired value of said second operating parameter; and,   secondary circuit means connected to said logic generator means for generating a drive signal for driving said second parameter means based on said output sequence signal.   
     
     
       2. The incubator of claim 1, further comprising: said sensing means being a first sensing means and said incubator;   second sensing means for sensing said second operating parameter and for supplying a third signal indicative of said second parameter; and,   said secondary circuit means being adapted to compare said third signal to said output sequence signal to generate said drive signal based on a comparison of said third and said output sequence signals until said third signal has changed to correspond to said desired value of said second operating parameter.   
     
     
       3. The incubator of claim 2, further comprising: a cot mounted on said base and adapted to hold the infant;   said circulating means being a blower mounted in said equipment compartment;   said first parameter means being a heater for heating the air circulated by said blower;   said second parameter means being a humidifier for imparting moisture to the circulated air;   said first sensing means being a temperature sensor for sensing the temperature of the circulated air as said first operating parameter; and,   said second sensing means being a humidity sensor for sensing the humidity as said second operating parameter.   
     
     
       4. The incubator of claim 1, further comprising: a circuit path connecting said primary control circuit means to said logic generator means; and, an interrupt switch connected into said circuit path for interrupting said circuit path thereby preventing said control value from reaching said logic generator means. 
     
     
       5. The incubator of claim 1, further comprising: a cot mounted on said base and adapted to hold the infant;   said circulating means being a blower mounted in said equipment compartment;   said first parameter means being a heater for heating the air circulated by said blower;   said second parameter means being a humidifier for imparting moisture to the circulated air; and,   said sensing means being a temperature sensor for sensing the temperature of the circulated air as said first operating parameter.   
     
     
       6. A method for controlling an environment for an infant in an incubator having a housing which includes a base and an enclosure mounted on the base for defining an enclosed space for accommodating the infant therein and wherein the environment for the infant is controlled, the method comprising: circulating the incubator air through said enclosed space;   imparting a first physical change to the environment within said enclosed space utilizing a first parameter means with said first physical change being measurable as a first operating parameter;   imparting a second physical change to the environment within said enclosed space utilizing a second parameter means with said second parameter means being measurable as a second operating parameter;   sensing said first operating parameter utilizing sensing means and providing a first signal indicative of the actual value of said first operating parameter;   supplying a second signal indicative of a desired value of said first operating parameter utilizing desired value generator means;   comparing said first and second signals and utilizing a primary control circuit means for driving said first parameter means to set and maintain said first operating parameter in dependence upon the comparison of said first and second signals;   defining a functional relationship between said first and second operating parameters utilizing a logic generator;   applying one of said first and second signals as a control value to said logic generator and utilizing said logic generator to generate an output sequence signal based on said functional relationship and said control value with said output sequence signal defining a desired value of said second operating parameter; and,   generating a drive signal in a secondary circuit connected to said logic generator and driving said second parameter means based on said output sequence signal.   
     
     
       7. The method of claim 6, wherein: said first parameter is the temperature in said incubator and said second parameter is the humidity in said incubator; and, the method includes the further steps of: storing values in said logic generator which determine the functional relationship between said incubator temperature and said humidity;   determining an operating point (A) on said functional relationship with said control value thereby determining a value pair (control value/sequence value); and,   changing said operating point (A) along said functional relationship in dependence upon the magnitude of said control value.   
     
     
       8. The method of claim 7, wherein: said values stored in said logic generator are stored in a multi-dimensional table having a dimension plane which is determined by the association of the said parameters of temperature and humidity defining first and second dimensions, respectively. 
     
     
       9. The method of claim 8, wherein: a third dimension is superposed on said dimension plane with said dimension being determined by a selected variable specific to the infant; and, a multi-dimensional logic function corresponding to this dimension is selected by determining said third dimension by inputting the selected variable. 
     
     
       10. The method of claim 7, wherein: said logic function has an upper limit value (HI) and a lower limit value (LO); and, a displacement of said operating point (A) takes place only parallel to said control value when said upper limit value (HI) is exceeded and when there is a drop below said lower limit value (LO). 
     
     
       11. The method of claim 6, comprising the further step of utilizing an interrupt switch to interrupt a circuit path between said primary control circuit and said logic generator.